Friction clutches can be provided with a power-controlled adjusting device to compensate for wear that occurs in friction linings. Here, an unfavorable wear-induced development of the clamping force of an actuating system operating on a counter plate of the friction clutch to move the pressure plate, for example a diaphragm spring, is detected, and an adjustment is made depending on the clamping force. Alternatively, an incorrect gap occurring between the clutch housing and the actuating system in connection with wear to the friction linings of the clutch plate can be ascertained (“sensed”), and corrected depending on the incorrect gap. To make the correction here, compensatory means situated between the counter plate and the actuating system, such as ramp systems or threading, are twisted.
A path-controlled adjusting device is known from EP 0 769 632 A2, in which a drive pawl of a sensing plate that moves axially with a diaphragm spring and a pressure plate, depending on the distance of an actuating system, acts on a pinion of an axially movable spindle, while a spindle nut held on the spindle pre-tensions a spring when the spindle is rotated, whereby, upon disengagement of the clutch, due to the axial displacement of the spindle, the spring twists a ramp ring of a ramp system situated between the pressure plate and the diaphragm spring relative to an opposing ramp of the pressure plate, thus restoring the original distance of the actuating system from the pressure plate. As this occurs, during the raising of a counter plate relative to the pressure plate, the drive pawl slides on the teeth of the pinion, and when a predefined wear has occurred, meshes with a gap between two teeth. The drive pawl carries the pinion with it by positive engagement, and at the same time rotates the pinion and hence the spindle, whereby the spindle nut is moved along the spindle and rotates the ramp ring by a corresponding angular amount, in order to thereby adjust the friction clutch. An additional locking plate engages with the pinion to prevent the pinion from turning back due to friction after an adjustment of the friction clutch.
There is a danger that the pawls engaging with the pinion may be damaged, which could impair the adjusting function of the adjusting device.